The present invention relates to a ballasted lamp socket for use with a gas discharge lamp, such as a fluorescent lamp. More specifically, the present application relates to a ballasted lamp socket for a compact fluorescent lamp suitable for replacement of an Edison screw-in socket in a conventional ceiling mounted light fixture, or a table or floor lamp.
Typically, gas discharge lamps, such as fluorescent lamps, must be driven by electronic ballasts in order to illuminate properly. Electronic ballasts receive an alternating-current (AC) line voltage from an AC power source, and generate a high-frequency AC voltage for driving the fluorescent lamps. The typical fluorescent lamp is a sealed glass tube containing a rare earth gas and having an electrode at each end for striking and maintaining an electric arc through the gas. The electrodes are typically constructed as filaments to which a filament voltage is applied to heat the electrodes, thereby improving their capability to emit electrons. Each filament requires two electrical connections, such that the filament voltage may be applied to the filament. Therefore, for a single fluorescent lamp having two filaments, four electrical connections (e.g., electrical wires) must be coupled between the ballast and the fluorescent lamp.
The use of compact fluorescent lamps (“CFLs”) has increased greatly over the last several years. These CFLs typically are more efficient and provide a longer operational life when compared to conventional incandescent lamps. Indeed, the recent spike in energy costs has lead to a greater demand for CFLs. In fact, in certain areas, such as California, for example, state law requires all new construction to be outfitted for the use of CFLs exclusively.
There are, however, some complications that have arisen with the increased use of CFLs. As an initial matter, most presently existing light fixtures are not compatible for use with CFLs. Specifically, the base of an incandescent lamp is substantially different than that of a CFL. Thus, the sockets in conventional light fixtures, which are generally referred to as Edison sockets, are not compatible with many CFLs.
FIG. 1 illustrates a conventional ceiling mounted downlight fixture 1000 that accommodates a conventional incandescent lamp (not shown). The fixture 1000 includes a housing 1004 in which a socket 1006 is mounted. In a preferred embodiment, a plurality of mounting clips 1008 are attached to the housing 1004 such that the fixture 1000 can be mounted in a ceiling, for example. A mounting clip, or clips, 1010 are provided on the socket 1006 to attach the socket to the housing 1004. A junction box 1012 is provided near the fixture 1000 with wires 1016a, 1016b extending from the junction box 1012 to the socket 1006 through a conduit 1014 to provide power to the socket 1006, and thus, the incandescent lamp mounted therein. The socket 1006 is illustrated as a conventional Edison socket with a threaded opening to accommodate the threaded base of the incandescent lamp. The socket 1006, however, is not structured to accommodate a CFL. Thus, one of the obstacles to using CFLs in many applications is the fact that current fixtures are not capable of accommodating CFLs.
Some manufacturers have produced modified CFLs that have been adapted to screw into Edison sockets. In this case, a modified base is provided with threads. This modified base is usually integral with one end of a body that includes a ballast circuit used to convert the electrical power provided by the wires 1016a, 1016b, for example, to a suitable voltage to drive the CFL. The lighted or lamp portion of such a modified CFL extends from an opposite end of the body. Alternatively, the modified base and the body with ballast circuit may be implemented as an adapter that screws into an Edison socket, and a receptacle may be provided in the body to receive a standard CFL. In this case, the modified base and body serve as an adapter for the CFL. In either case, the inclusion of the body inside the housing 1004 of the fixture 1000, for example, takes up space that would normally be used to ensure that the light source, whether it be an incandescent lamp or a CFL remains recessed within the fixture 1000. Thus, when such a modified base and body is used, a portion of the CFL ordinarily extends out of the fixture and is clearly visible below the ceiling. This ruins the aesthetic appeal that is one of the major advantages of fixtures such as the downlight fixture 1000 described above.
There are light fixtures that are structured for use exclusively with traditional CFLs. In fact, in many locations, where CFL use is required, there is often a requirement to install such exclusive CFL fixtures so that users cannot substitute less efficient incandescent lamps for everyday use. For example, many fluorescent lamps require specific fluorescent lamp sockets that are different from standard screw-in Edison sockets for incandescent lamps. Further, these fluorescent light fixtures typically require that the ballast be mounted external to the light fixture, e.g., in the junction box 1012. Accordingly, at least four electrical wires must be provided through the conduit 1014 between the ballast in the junction box 1012 and the fluorescent lamp in the fluorescent socket in the fixture 1000, such that the ballast is able to provide the appropriate filament voltages to the filaments of the lamp. As a result, the power supplied from the ballast to the filaments of the lamp must travel over a relatively long distance from the junction box 1012 to the fluorescent lamp socket. This relatively long distance results in an undesirable increase in electromagnetic interference (EMI) and undesirable parasitic effects due to current leakage and capacitive coupling with the conduit 1014, for example.
Further, difficulties arise when a CFL is used in conjunction with a standard phase-control dimmer switch. An incandescent lamp can be dimmed simply by reducing the amount of power supplied to the incandescent lamp, e.g., by driving the incandescent lamp with a phase-controlled voltage as is well known to one of ordinary skill in the art. However, when a CFL is driven with a phase-controlled voltage, the CFL typically cannot be dimmed to a low light level. Often, the CFL completely turns off once the CFL is dimmed below a certain level. As a result, most CFLs cannot be dimmed below approximately 20% of their maximum light output when used with contemporary dimmer switches. Indeed, even many so-called “dimmable” CFLs or CFL adapters do not actually allow for dimming below a 20% threshold. Naturally, this performance limit is not desirable.
Accordingly, it is be desirable to provide a lamp assembly for a dimmable CFL for use in a ceiling mounted light fixture that avoids the problems discussed above.